Hummingbird Image Score Still Low After Smush Image Compression

Hello - I've compressed all images in my media library using Smush, but am still getting a 6/100 on image compression. Hummingbird is recommending I compress several images, but these images are already compressed (I don't have the option to do so again) according to Smush.

Google Page Insights is also penalizing us badly for images so I believe this issue relates to the compression itself, not hummingbird.